Button of Choice: Use ToggleButtons as RadioButtons

For MQTT.fx I wanted to use ToggleButtons to e.g. choose the de coding of a MQTT Message or the QoS Level:   I found out that in context of a ToggleGroup ToggleButtons behave different than RadioButtons in terms of selection/deselection: unlike RadioButtons ToggleButtons can still be set to unselected state.   A RadioButton extends ToggleButton and overrides fire() (which is…